Anonymous inner class

This is an example of how to use an anonymous inner class inside a class. In order to use an anonymous inner class we are using the javax.swing package to create a window with a button:

  • We create a new JButton that is an implementation of a “push” button with the message “Close Window”.
  • A new ActionListener object is created that overrides the actionPerformed(ActionEvent event) of the ActionListener interface. This method will be invoked when the action will occur and it calls exit(0) API method of System to end the application.
  • The ActionListener is added to the JButton, with addActionListener(ActionListener l) API method of JButton.
  • A new JFrame is created and the button is added to it, with add(Component comp) API method of JFrame.
  • Then its size is set, with setSize(int width, int height) API method of JFrame.
  • We also set the operation that will happen by default when the user initiates a “close” on this frame, that is one of the constants provided by JFrame. The selected operation is JFrame.EXIT_ON_CLOSE.
  • Then the frame is set to visible, with setVisible(boolean b) API method of JFrame. A new window is created with a button that has the given message. When the user presses the button the frame is closed.

Let’s take a look at the code snippet that follows:

package com.javacodegeeks.snippets.core;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;

public class AnonymousClass {

    public static void main(String[] args) {

  JButton closeWindow = new JButton("Close Window");

  closeWindow.addActionListener(new ActionListener() {


public void actionPerformed(ActionEvent event) {




  JFrame frame = new JFrame();


  frame.setSize(300, 200);



This was an example of how to use an anonymous inner class inside a class in Java.

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Byron Kiourtzoglou

Byron is a master software engineer working in the IT and Telecom domains. He is an applications developer in a wide variety of applications/services. He is currently acting as the team leader and technical architect for a proprietary service creation and integration platform for both the IT and Telecom industries in addition to a in-house big data real-time analytics solution. He is always fascinated by SOA, middleware services and mobile development. Byron is co-founder and Executive Editor at Java Code Geeks.
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